Once hailed as the energy source of the future, biofuels have lost some lustre because of their dubious sustainability. Here we take a look at the latest figures for some of the main energy crops. Caroline Morley

Sugar can provide high-energy fuel for machines as well as people. For biofuel, it comes from sugar cane, which is mostly grown in tropical regions. Distilling the juices creates bioethanol, which can fuel vehicles. The residues, known as bagasse, and the cane straw can be burned to produce bioelectricity.

Brazil is the world's main producer of sugar cane. In that country, petrol is legally required to contain at least 22 per cent bioethanol. There is also a push towards generating more bioelectricity. According to the Brazilian Sugarcane Industry Association (UNICA), Brazil produced over 487 million tons of sugar cane in the 2007/08 harvest period from fields occupying about 7.8 million hectares – about 2 per cent of all arable lands available in the country.